In current practice of dermal analysis and of oral and dental lesion analysis, the physician typically observes the suspected area with the naked eye, or more rarely with an episcope to illuminate the skin, and based on parameters of size, color and other aspects of the visual appearance, decides whether the lesion warrants further observation, medical tests or treatment. The examination and diagnosis are therefore highly subjective, and are dependent upon the medical practitioner's powers of observation and experience.
Occasionally the practitioner will recommend follow up observation in order to ascertain that no changes in size or coloration of the lesion have occurred. These changes suggest malignancy or other pathologies, such as inflammation. Typically the practitioner will record the general appearance, size (diameter) and color in his records. When the patient returns for the follow-up visit, reference will be made to these records, which are not always sufficiently detailed in order to allow proper comparison.
For instance, when the color is recorded, it is significant for diagnosis if changes have occurred in the intensity of the color, and the practitioner has no efficient means of recording or analyzing the color changes that occurred over time. Some medical practitioners have begun to record and retain an image of the lesion using a digital camera, in order to refer back to this image upon subsequent visits. The practitioner will usually try to photograph from a predetermined distance at each instance, so that the size of the lesion appears similar, as does the angle from which the image is recorded. Comparison is then performed by visual assessment of the recorded image, versus a more current image, or versus the physical lesion itself during examination.
However, the images are influenced by the ambient lighting present in the room, which changes during different times of the day and in different seasons. The images are similarly influenced by the specific camera and flash used. These affect the appearance of the digital image, and hinder comparison of the images, especially in regard to the color changes occurring.
Two early prior publications address this problem. WO97/47235, by the inventor, discloses use of a reference label containing reference colors, which is placed near the lesion, then photographed using any type of digital camera. The colors are then normalized according to this reference label, using computer processing, in order to eliminate the effect of changes in the ambient lighting. After normalization, the colors of the lesion can be compared to color-normalized images previously recorded.
U.S. Pat. No. 5,852,675 to Matsuo et al. similarly discloses various reference labels and algorithmic means of their computerized detection and analysis, which aim to eliminate the effect of changes in the ambient lighting, upon the color of digitized images. In addition to normalization of the colors, the labels disclosed in both U.S. Pat. No. 5,852,675 and in WO97/47235 allow normalization of the size and skew of the image.
A later publication, WO01/35827, discloses a handheld episcope for dermal lesion viewing, having a cone of reference colors to allow color normalization, and a video or digital camera inside the unit. Recording of the images is performed either by inclusion of a memory chip or by connection of the unit by cables to a computer. Normalizations are performed of the color, the size and skew of the image.
Even after normalization of the colors of digitized images, the comparisons performed in the prior art do not help determine how the colors have been affected over time. This is important for instance, in analysis and diagnosis of oral images, where lesions in which the color becomes more intensely red over time can signify malignancy, infection or inflammation. Reduction in the intensity of the redness can signify healing and a positive reaction to treatment. Changes in the color intensity of a dermal lesion that becomes more brown, or more intensely gray, can signify melanoma. Since the analysis of the degree of change is most often performed visually, it is highly subjective and inaccurate.
Even when the digitized image is analyzed using computer processing such as described in the aforementioned documents (WO97/47235 and U.S. Pat. No. 5,852,675), the processing and analysis focuses on determining whether changes in the size of the lesion occurred, such as border enlargement.
In WO97/47235, the analysis pertaining to changes in color allows the user to determine how many pre-selected points in the lesion underwent changes in color over time, however there is no means of quantifying the intensity of these color changes, and therefore there is no way to determine whether the changes are significant enough to warrant biopsy or further observation. Slight changes in color do not necessarily indicate activity in the lesion, and could be related for instance to tanning of the skin.
Additional measurements pertaining to color, which were disclosed in WO97/47235 relate to the average color of the entire lesion, which could be plotted as a histogram. Such a histogram does not help the physician establish whether the color intensity has changed to a significant degree at particular points within the lesion.
To date, there is no way in prior art to calculate and quantify whether a specific area of tissue or organ has become more intensely colored, signifying a suspected malignancy or inflammation.
Therefore, the need exists for an objective and quantitative method of analyzing the aspects of color present in a lesion. Such a tool would allow images to be compared and analyzed without being influenced by changes in the ambient light, and would grant the user a means of quantifying the color in the lesion, in order to determine the degree of change which has occurred in the lesion, and whether the changes are sufficiently significant to indicate malignancy or other undesirable biological changes are present. The method would allow evaluation of the degree of response to treatment, or of the degree of spontaneous healing of the lesion.